Description of problem:

"virt-manager" wrongly set <driver name> to "file" instead of "qemu" when attaching a virtual cdrom disk to the VM by clicking "connect/disconnect" button, and VM fails to start with following trace back.

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/engine.py", line 501, in run_domain
    vm.startup()
  File "/usr/share/virt-manager/virtManager/domain.py", line 575, in startup
    self.vm.create()
  File "/usr/lib64/python2.4/site-packages/libvirt.py", line 333, in create
    if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: internal error unsupported driver name 'file' for disk '/vm/ISO/rhel-5-server-x86_64-dvd.iso'

Environment:

virt-manager-0.6.1-13.el5
libvirt-0.8.2-15.el5_6.1
RHEL 5.6 KVM

How reproducible:

- Click Add Hardware and add a new cdrom drive attached to an iso image.
- verify that the <driver name> is set correctly to "qemu"

<disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/vm/ISO/rhel-5-server-x86_64-dvd.iso'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='1' unit='0'/>
    </disk>

- Now shutdown the VM
- Select "cdrom" and click "disconnect" button and disconnect the ISO image from drive.
- Click "connect" button and connect the ISO image back to the drive.
- Check xml configuration and see that <driver name> is changed to "file" at this time.

<disk type='file' device='cdrom'>
      <driver name='file' type='raw'/>
      <source file='/vm/ISO/rhel-5-server-x86_64-dvd.iso'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='1' unit='0'/>
    </disk>